Sustainable tourism – Crown of thorns outbreaks

Sustainable tourism – Crown of thorns outbreaks

Similarly to our pacific neighbours, New Caledonia has experienced large outbreaks of Crown of thorns (Acanthaster solaris) in the past decades. Recent studies from the French IRD seems to indicate that outbreaks are intensifying.

At Oleti Tours, as an actor of sustainable tourism in New Caledonia, we wanted to share the latest state of knowledge regarding the acanthaster and give some advice if during your dive or snorkelling on a New Caledonian reef you observe an outbreak of the starfish:

DO NOT TOUCH THE ACANTHASTER: first, its horn-like spines that cover its upper surface are venomous and you might hurt yourself (even trough gloves). Second, when stressed they are likely to release gametes and increase reproduction levels.

DO NOT TRY TO KILL THEM: the acanthaster is able to regerate itself and if for example you cut it, you might generate 2 starfish instead of 1

What do we know about the acanthaster?

The acanthaster is a normal component of reef ecosystems and you can normally find a few crowns of thorns per hectar of reef. They are said to preferentially eat fast growing coral, therefore contributing to a balance between slow growth and fast growth coral.

The problem we have is with the outbreaks of acanthasters that we observe now. Little is known about the causes of this issue: causing factors include a deterioration of the quality of water, warming of the ocean.

A reduction of the numbers of predators is also a possible contributing factor though it doesn’t seem to be a main cause as the predators have only a limited capacity to eat acanthasters. Predators of the acanthaster, include the triton’s trumpet (conque ou toutoute in French), as well as some putterfish and triggerfish.